1. Field of the Invention
The present invention relates to mirrors and more particularly to rear or side view mirrors for transportation vehicles, such as automobiles, boats, trains, aircraft, and especially trucks and buses.
2. Background Information
The necessity for rear view mirrors on vehicles such as trucks, municipal buses, school buses, and recreational vehicles has long been apparent. Drivers must see from the normal driver's position the reflections of objects such as other vehicles, the roadbed and obstructions outside the restricted limits of direct vision. On large vehicles, the mirrors are normally positioned on the exterior of the body, as the view directly behind the driver is usually blocked by either interior components of the vehicle or exterior components such as a trailer. It is advantageous for vehicle mirrors to be adjustable to accommodate the changing need of drivers to view different areas around the vehicle, to accommodate different drivers, and in the case of articulated vehicles to keep the rear of the vehicle in view during turning maneuvers.
The mirrors most suitable for this purpose must possess a number of attributes. They must provide a usable image even when subjected to the vibration and shock concomitant with usage on heavy vehicles. They must maintain their position when subjected to the forces of the wind, vibration and shock for long periods of time. They should be mechanically durable and resist the effects of the environment such as road salt, vehicle wash acid, water, ice, and extreme of temperature variations. Another type of durability that is advantageous is the ability of the adjustment system to resist damage when operated against a load, i.e. not suffer damage if operation is attempted when the mechanism is frozen with ice or if the mechanism is operated accidentally against the limits of travel for an extended period of time, such as an object inadvertently falling against the switch in the cab of a truck. It is most convenient for the mirrors to be remotely adjustable from the drivers normal position behind the steering wheel. It is also a great advantage if the mirror can be manually adjusted should there be a failure of the remote adjusting system. This is both for safety reasons and because the current law in many states requires that the mirrors on heavy vehicles be serviceable if the vehicle is to be operated on the highways of a state or other governmental entity.
Perhaps the simplest and oldest method of remotely adjusting rear view mirrors on the outside of a vehicle is to provide the operator with a mechanical device, such as a wire cable inside a tightly wound steel spring that is connected to an appropriate point on the plate the mirror is mounted upon. Variations on this theme have been patented as recently as 1988 and 1989 (Riley, U.S. Pat. No. 4,784,011; Polzer, U.S. Pat. No. 4,856,886; and Seitz, U.S. Pat. No. 4,863,255). While economical, these types of systems do not permit the ease of precision adjustments demanded by discerning users and tend to be subject to vibrations to the point of being unusable on heavy vehicles. These shortcomings have resulted in a number of more sophisticated (and more expensive) designs.
The most common type of drive system for remote controlled mirrors uses one or more electric motors. The number of U.S. Patents using this power source is a testament to the popularity of electric motors. These patents include Baird, U.S. Pat. No. 3,005,384; Bateman, U.S. Pat. No. 3,610,736; Lafont et. al., U.S. Pat. No. 4,245,893; Oskam, U.S. Pat. No. 4,281,899; Deshaw, U.S. Pat. No. 4,286,841; Albrecht et. al., U.S. Pat. No. 4,295,708; Stelma, U.S. Pat. No. 4,341,444; Hewitt, U.S. Pat. No. 4,456,333; Weber, U.S. Pat. No. 4,464,016; Weber et. al.,U.S. Pat. No. 4,519,677; Bramer, U.S. Pat. No. 4,701,037; Lang et. al., U.S. Pat. No. 4,991,950; Vercesi et. al., U.S. Pat. No. 5,020,896; and Mittelhauser, U.S. Pat. No. 5,059,014. Irrespective of their popularity, electric motors have many problems. These include greater weight and cost, the necessity of a heavy and complex gear reduction system, greater space requirements, the propensity of electric motors to burn out when subjected to high loads for extended periods of time, and the susceptibility of electrical systems to vehicle wash acid and road salt.
The problems with electric motors have inspired a number of other inventors to attempt improvements upon the electric systems by using hydraulic or pneumatic cylinders. Designs using these power sources are detailed in U.S. Patents by Stanfield, U.S. Pat. No. 3,624,818; Rogers, U.S. Pat. No. 3,650,607; House, U.S. Pat. No. 3,815,365; Brewington, U.S. Pat. No. 3,825,324; Pierce, U.S. Pat. No. 4,364,638; and An, U.S. Pat. No. 5,035,496. Similar power sources are the bellows or bladder designs described in U.S. Patents Hess, U.S. Pat. No. 3,873,190; Mittelhauser, U.S. Pat. No. 4,732,463 and U.S. Pat. No. 4,768,871; and Duroux, U.S. Pat. No. 4,918,920. While offering some advantages, such as the ability to be operated against a stalling load for long periods of time, these pneumatic or hydraulic systems are susceptible to leakage, and must maintain a constant pressure in order to maintain position and to prevent the mirror from inadvertently changing position.
In an attempt to solve all of the above problems, Victor Riccio developed a design using an externally mounted blower wheel and gear train, disclosed in U.S. Pat. No. 3,687,525. The gear train rotates a vertical shaft attached to the mirror. Due to its bulky shape, the power train is external and exposed to the elements. The line of power transmission makes a 90 degree turn, and has three gear interfaces between the vertical mirror shaft and the worm gear. In a gear train such as this, regardless of application, the worm gear is the entity that prevents movement of the mechanism when force is applied from the reverse direction. In the design of externally mounted rear view mirrors it is of critical importance that the extreme vibration encountered, due to the engine and the movement of the vehicle over uneven road surfaces, has minimal transmission to the rear view mirrors. It is apparent that the aforementioned three gear interfaces would allow considerable movement before being stopped by the worm gear, and it can inferred that a mirror so designed would have grossly unacceptable vibration and movement characteristics (position creep) when in operation on heavy vehicles. Still another problem with this design is that a system that rotates a vertical center shaft is not appropriate for a mirror that rotates in more than one axis.